title: Anomalous viscosity effect in the early stages of the ion-assisted adhesion/fusion event between lipid bilayers: a theoretical and computational study.
abstract: The effect of viscosity on the encounter rate of two interacting membranes was investigated by combining a non-equilibrium Fokker-Planck model together with extensive Molecular Dynamics (MD) calculations. The encounter probability and stabilization of transient contact points represent the preliminary steps toward short-range adhesion and fusion of lipid leaflets. To strengthen our analytical model, we used a Coarse Grained MD method to follow the behavior of two charged palmitoyl oleoyl phosphatidylglycerol membranes embedded in a electrolyte-containing box at different viscosity regimes. Solvent friction was modulated by varying the concentration of a neutral, water-soluble polymer, polyethylene glycol, while contact points were stabilized by divalent ions that form bridges among juxtaposed membranes. While a naïve picture foresees a monotonous decrease of the membranes encounter rate with solvent viscosity, both the analytical model and MD simulations show a complex behavior. Under particular conditions, the encounter rate could exhibit a maximum at a critical viscosity value or for a critical concentration of bridging ions. These results seem to be confirmed by experimental observations taken from the literature.
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy. araudino@dipchi.unict.it
authors.forename: Antonio
authors.initials: A
authors.lastname: Raudino
authors.forename: Siewert J
authors.initials: SJ
authors.lastname: Marrink
authors.forename: Martina
authors.initials: M
authors.lastname: Pannuzzo
mesh_terms: D003198:Computer Simulation; D007477:Ions / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008962:Models, Theoretical; D056004:Molecular Dynamics Simulation; D011108:Polymers / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D007477:Ions; D008051:Lipid Bilayers; D011108:Polymers; D012997:Solvents; D014867:Water